With the increase in the flow of information and the popularity of computers, the computer is being used more extensively for processing external information. Currently, there is a trend towards using a computer as a telephone, a facsimile machine, and/or an answering machine. The computer typically implements telephone functionality by incorporating the analog circuitry found in a common telephone. Alternatively, a computer can use a modem in order to receive and transmit telephonic information.
For data transmission on a standard voice grade telephone line a modem may be employed to modulate data in a form suitable for transmission along the telephone line, and to demodulate data received from the telephone line in order to reproduce the data transmitted from a remote site for use in the computer. A modem modifies a digital signal for transmission over an analog medium. More specifically, it converts serial digital data for transmission over a carrier signal by changing the phase, frequency and amplitude of the signal.
The term "modem"(modulator-demodulator) normally refers to an auto-dialing, auto-answering modem that may be external or internal relative to the computer. An external modem is a stand alone device having one connector for coupling to the telephone lines and another connector for coupling to an I/O (input/output) port of the computer. The I/O port is commonly an RS-232 interface, which has become an industry standard for asynchronous serial communications in microcomputer devices. The RS-232 interface specifies a set of control signals and voltage levels (nominally +/-12 volts).
An internal modem may be built into the computer enclosure and may even be present on a circuit board or inside an integrated circuit. In either case, the modem and the computer exchange a number of control signals according to a specific protocol so as to condition the modem to accept incoming data calls or to place outgoing calls.
Whether or not a modem is used, if the computer is being used as a telephone, problems may develop if the computer also uses a power management system. With the advent "Green Machines" and power consumption concerns in desktop PC's, most computers now implement some form of power management. This power management is most frequently based upon the detection of "activity", where activity is commonly defined as some sort of interrupt and may include system and user activity. However, there is no simple method for identifying activity when the computer is being used only for its telephone functionality.
A conventional telephone may be a hand telephone set in which the hand set of the telephone is supported on a mounting (or body of the telephone). Typical among these telephones is the hang-up hand telephone set (also suspended-type handset telephone, bracket-type handset telephone) in which the mounting is attached to a vertical surface (such as a wall) and has a switch bracket from which the hand set is suspended. Typically, this switch bracket takes the form of, and is called, a "hook".
The user first initiates a telephone call or receives a telephone call by lifting the hand set from the hook. At this point, the telephone is considered to be in an "off-hook" state. When in this "off-hook" state the user may be dialing, on hold, or transmitting or receiving voice data. The concept of a telephone being in an "off-hook" state may also be applied to a telephone without a hook, a facsimile machine, an answering machine or the like. In other words, once the telephone or similar device picks up the line in response to an incoming call or picks up the line in order to transmit information the telephone is considered to be in "off-hook" state. During this off-hook state it would be undesirable for power to be cut off to the telephone device because that would terminate the transmission of voice or other data.
A power management system within a computer for conserving power typically uses a power management unit (PMU) to shut down power to the computer in stages if no activity is detected. There are a wide variety of actions that may constitute computer activity. By way of example, one such computer activity is user activity. User activities are actions produced by a person that indicates that a person is present at the computer and as such the computer should not be shut down. Actions such as keystrokes, moving the mouse, speaking, touching the computer screen, or other actions by a person may constitute user activity. This user activity is detected by the computer and by the power management unit which then will not shut down power to the computer when such activity is detected. It is common for a power management unit to shut down power to a computer after a predetermined time if no activity is detected. For example, a power management unit may begin shutting down power to a computer in stages if no activity is detected after two minutes. If activity is detected within those two minutes, power will not be shut down.
Computer activity also includes any kind of general system or CPU activity. In other words, the PMU will not shut down power to the computer if certain types of CPU activity are detected. For example, if the CPU is processing data, printing or performing other functions, the PMU will detect this activity and will not shut down power to the computer.
As mentioned above, if no activity is detected by the PMU, the PMU may begin to shut down and conserve power within the computer in stages. The stages of power shut down within a computer generally mean shutting, down those processes that consume the most power first. For example, if the PMU determines that no activity has been present for a predetermined amount of time, in a first stage of shut down the PMU may turn off power to the computer monitor. As the computer monitor generally uses the most power within a computer it is more likely to be turned off first. However, for a laptop computer the monitor may not necessarily be powered down first because it may not be the most energy intensive part of that computer. In a second stage of power shut down the PMU may start to cut back on system activity. For example, the CPU system clock or clocks may be throttled back to a lower frequency. For example, a 75 MHz clock may be reduced to operating at a 25 MHz frequency. Next, the PMU may a ctually turn off the clock for periods of time. The clock may be turned off between keystrokes or between other indicators of user activity. Finally, the PMU may turn off the system clock all together.
In a third stage of power shut down the PMU may begin to turn off power to various sub-systems within the computer. For example, the PMU may shut down power to a printer interface card, a PCMIA card, or may stop the spinning of the hard disk, etc. Finally, the PMU may shut down all power to th computer completely by cutting off power available from a power source within the computer. In this fashion, it should be appreciated that the PMU may shut down power to a computer and its associated hardware in various stages. Any one of these various stages may be considered a reduced power or power saving mode of the computer or CPU.
A problem may occur if the computer is being used as a telephone and is currently enabled for power management. The computer may not recognize that there is activity ongoing, and may shut down power to the computer and to the telephone device while the user is engaged in a conversation. Likewise, if the computer is being used as a facsimile machine or as an answering machine or the like, if the power management system does not recognize this use as a traditional activity, power may also be shut down, thereby abruptly terminating those activities.
If the computer is being used as a telephone in voice mode, the central processing unit (CPU) is typically bypassed and may not show any activity, i.e., a separate analog, telephone circuit may be in use and the CPU will not be involved. If so, this analog telephone circuitry may not produce activity that can be detected by a power management unit (PMU), and the power management unit may shut down power to the computer. The PMU is circuitry typically within a chip set of a computer (i.e. chips that support the functionality of the CPU) that implements the power management system of the computer. If the power is shut down to the computer the telephone circuitry may cease to function and the telephone line may also be hung up.
Accordingly, for a computer with a power management system, a simple, cost effective method is desired for keeping power supplied to the computer while the computer is being used as a telephone.